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How Surface Roughness Affects the Light-Scattering Properties of Ice Crystals

The size and shape of ice crystals are known to affect the light scattering properties of clouds; with implications for both weather and climate. Less known, however, is how the roughness of ice crystals impacts light scattering.

Research in the Journal of Geophysical Research reveals a new method for growing and manipulating ice crystals in a laboratory, which allows for analysis of their roughness. The team defined a measure of roughness and described a method for inferring its value. The research shows that that the 22-degree halo effect—a halo seen around the Sun or other light source when light is refracted by hexagonal ice crystals—still occurs even when these crystals have rough prismatic facets.